Products, such as plastic bottles, containers and other products can be made using a number of techniques depending on the requirements of the product. Products, including bottles and containers may be made using multiple techniques if, for example, different materials must be used or different functions are required. For example bottles are generally made by either i) extrusion blow molding, wherein a parison is made by extruding molten material around a mold composed of 2 separate cavities, trapping a free end, forming a hollow area between the cavities and then blowing air through the parison, pushing it towards the cavities walls and making the bottle shape, or ii) first injection molding a preform, often resembling a test tube shape with a collar area, wherein the screw thread of the bottle is formed on the outside of the collar area, then the preform is moved to a different production unit and is blown to make the bottle. Most plastic bottles used as packaging containers have an outside-facing thread or other closure or finish etc on the neck portion, to which a cap may be fitted. This outside-facing thread can be formed by using a split mold, comprising at least two mold components, when either forming the parison or injecting a preform.
When developing caps for attachment to bottles with outside-facing thread, the screw thread thereof, must be on the inside of the cap in order to be able to connect with the screw thread on the outer surface of the neck of the bottle. In this context, the inside facing thread, is delivered by transfer moulding from an outer-facing thread pattern formed on the outer surface of a core mold component. Therefore, after production, the core would need to be disengaged from the finished product. Disengaging the core from the finished article may be done so by rotating the core, and moving it in the axial direction. Therefore, the rotation and the axial moving should be synchronized. However, the synchronizing action mechanically limits the speed of production and synchronization can be poor, resulting in damage to the formed thread. Moreover, since the thread is prepared using heated material, when pulling out the core, the thread can be damaged. An alternative to the above method, is where instead of rotation and axial movement of the product, it is simply pulled from the core using mechanical force. Whilst this system of disengagement of the product from the mould is simple and quick, it may result in damage to the thread, resulting in a poor connection points and potential leakage when joined with a bottle. Moreover the shaping of the thread itself must use minimal height thread and rounded corners in order to allow the mechanical ‘bump-off’ release. These latter features result in poor connection between bottle and cap, mispositioning of the cap during screwing, low maximum application torque, and potential leakage. A further known method of making inner thread products consists in molding the cap in a one step injection molding process, by using a collapsible core which molds all the inner surfaces. At the end of the injection molding cycle, the core retracts, so that its undercut portion can be ejected through the bottom part of the dosing cylinder which has a restricted diameter. The major disadvantages in molding a dosing cap with undercut using collapsible cores, are that the production speed is slow and the collapsible cores are fragile, they are worn out/broken easily, resulting in frequent halts to production, changing of tools, reduced tool capacity and cost escalation.
Dosing devices in the past have generally fitted onto the cap. They are generally not attached to the bottle or cap other than through friction of the dosing device on either cap or bottle. Manufacturing a separate cap and dosing device is clearly not economical, requiring further process and production equipment, space in plant and additional materials. Moreover the process is slowed due to the need to not only fit a cap to a bottle, but also a dosing device.
It has been the Applicants objective to combine the requirements of the cap and dosing device to one product, which can then be subsequently connected to a bottle and develop a method of making such a device which is efficient and economical and permits varied dosage sizes.